Guide:Reducing lens complexity

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TODO: this article needs to be expanded for edge cases like already low diopters.

When to reduce lens complexity

Lens Complexity is best reduced before getting into the low diopters range. Ideally, normalized correction for both eyes should be simple and equal by the time a low diopters range (e.g. -1.5 diopters)[1] is reached.

How to reduce lens complexity

Make your first reduction or two simple and spherical. This will teach you the basics of the EndMyopia methods.

There are two types of reductions:

  • A simple reduction or binocular reduction is drop in lens powers for both eyes, simultaneously
  • An equalizing reduction or monocular reduction is drop in lens power for one eye, the eye with greater correction (more negative)

An equalizing reduction is done to bring the eyes closer to having the same level of correction. Jake said that "...if you do reduce the ratio, you should have at least 2 regular spherical reductions in between."[2] This is not always possible, especially when high anisometropia is involved.

There are three types of reductions with respect to the power change:

  • a 0.25 D drop to spherical power
  • a 0.25 D drop to cylindrical power
  • a trade of 0.5 D cylindrical power for 0.25 D spherical power

There are four rules for reducing complexity:

  1. Alternate types of reductions. Have one (Simple > Equalizing > Simple > Equalizing...) or two (Simple > Simple > Equalizing > Simple > Simple > Equalizing...) simple drops between equalizing drops.
  2. Change only spherical or only cylindrical and never both simultaneously.
  3. For an equalizing reduction, change both differential lenses and normalized lenses simultaneously to keep the focal planes in sync.[3]
  4. For a simple reduction, change differential lenses a few weeks after normalized lenses to keep changes to focal planes to a minimum.


A note on rule 3 and rule 4: Keeping focal planes in sync is a higher priority than keeping changes to focal planes to a minimum, thus rule 3 exists.

Example Spherical Reduction Schedule
Reduction Type Normalized Differentials Explanation
Left Right Left Right
-3.50 -4.00 -2.25 -2.75 This is the starting point.
wait 8 - 16 weeks
Simple -3.25 -3.75 Perform normalized reduction.
wait 4 - 8 weeks (rule 4)
-2.00 -2.50 Perform differential reduction.
wait 4 - 8 weeks
Equalizing -3.25 -3.50 -2.00 -2.25 Both norms and diffs are reduced simultaneously. (rule 3)
wait 8 - 16 weeks
Simple -3.00 -3.25 Perform normalized reduction.
wait 4 - 8 weeks (rule 4)
-1.75 -2.00 Perform differential reduction.
wait 4 - 8 weeks
Equalizing -3.00 -3.00 -1.75 -1.75 Both norms and diffs are reduced simultaneously. (rule 3)
wait 8 - 16 weeks

References

See also